Wheel and tire assembly

ABSTRACT

A wheel assembly is disclosed, the wheel assembly including a rigid wheel including a radially outer rim wall presenting a polygonal shape with a plurality of outermost vertices connecting a plurality of planar faces, and a flexible tire mounted on the outer rim wall. The tire is supported by the vertices of the rim wall and is separated from the rim faces by a space, portions of the tire located between the vertices being configured to flex inwardly when subject to ground engaging pressure.

BACKGROUND

1. Field

Embodiments of the present invention relate to wheel and tire assembliesfor use with airless tires. More particularly, embodiments of thepresent invention relate to airless wheel assemblies with certainperformance characteristics of pneumatic tires.

2. Related Art

Irrigation systems include elevated water conduits supported by mobiletowers. Such mobile towers are mounted on wheels that propel the towersalong the ground to be irrigated. The wheels typically include pneumatictires that require periodic maintenance, including adjusting airpressure, repairing tires that develop holes or other damage, andreplacing old or damaged tires that are beyond repair.

Because irrigation systems and similar agricultural equipment aretypically used in fields or other remote locations, monitoring the tiresfor problems and reaching the tires to perform maintenance and repairscan be inconvenient or difficult. If a tire loses air pressure and isnot repaired in a timely manner, damage to the tire, to the equipmentmounted on the tire, or both may result.

One solution to the challenges presented by the use of pneumatic tiresinvolves using wheels without tires. While this approach addresses mostof the problems of tire maintenance, repair and replacement, it presentsother challenges. Tireless wheels, for example, are rigid and experiencegreater ground penetration than a flexible tire, thereby creating rutsor otherwise disturbing the land more than a pneumatic tire.

Similar problems exist for tractors, automobiles, and other vehiclesthat typically use pneumatic tires.

Accordingly, there is a need for a solution which overcomes thelimitations described above.

SUMMARY

A wheel assembly in accordance with an embodiment of the inventioncomprises a rigid wheel including a radially outer rim wall presenting apolygonal shape with a plurality of outermost vertices connecting aplurality of planar faces, and a flexible tire mounted on the outer rimwall. The flexible tire is supported by the vertices of the rim wall andis separated from the rim faces by a space, and portions of the tirelocated between the vertices are configured to flex inwardly whensubject to ground engaging pressure.

A wheel assembly in accordance with another embodiment of the inventioncomprises a rigid wheel including an inner hub and a plurality of spokeelements extending radially outwardly from the hub, and an outerflexible airless tire mounted on the wheel such that the tire issupported by the spoke elements, portions of the tire located betweenthe spoke elements being configured to flex inwardly when subject toground engaging pressure.

A mobile irrigation system tower in accordance with yet anotherembodiment of the invention comprises a structure for supporting anirrigation system conduit, and a plurality of wheel assembliessupporting the structure. Each wheel assembly includes a rigid wheelincluding a radially outer rim wall presenting a polygonal shape with aplurality of outermost vertices connecting a plurality of planar faces,and a flexible airless tire mounted on the outer rim wall such that thetire is supported by the vertices of the rim wall and is separated fromthe rim faces by a space, portions of the tire located between thevertices being configured to flex inwardly when subject to groundengaging pressure.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Other aspectsand advantages of the present invention will be apparent from thefollowing detailed description of the preferred embodiments and theaccompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary irrigation system includingwheel assemblies constructed in accordance with embodiments of theinvention;

FIG. 2 is a first side perspective view of one of the wheel assembliesof FIG. 1, the wheel assembly including a rigid wheel and a flexibleairless tire mounted on the wheel;

FIG. 3 is a second side perspective view of the wheel assembly of FIG.2;

FIG. 4 is a perspective fragmentary view of the wheel assembly of FIG.2;

FIG. 5 is an exploded view of the wheel assembly of FIG. 2;

FIG. 6 is a side elevation view of the wheel assembly of FIG. 2,illustrating the wheel assembly mounted on the irrigation system of FIG.1 and the tire flexing in response to ground engaging pressure;

FIG. 7 is a side perspective view of a wheel assembly constructedaccording to another embodiment of the invention, the wheel assemblyincluding a rigid wheel with a polygonal outer rim wall and a flexibleairless tire mounted on the wheel;

FIG. 8 is an exploded view of the wheel assembly of FIG. 7;

FIG. 9 a is a side elevation view of the wheel assembly of FIG. 7,illustrating the wheel assembly mounted on the irrigation system of FIG.1 and the tire flexing in response to ground engaging pressure;

FIG. 9 b is a side elevation view of the wheel assembly of FIG. 9 a, thewheel assembly including spacers between the wheel and the tire, thespacers limiting the amount the tire flexes in response to the groundengaging pressure;

FIG. 10 is a side perspective view of a wheel assembly constructedaccording to another embodiment of the invention, the wheel assemblyincluding a rigid wheel presenting a hub and spoke configuration and aflexible airless tire mounted on the wheel;

FIG. 11 is an exploded view of the wheel assembly of FIG. 10;

FIG. 12 a is a side elevation view of the wheel assembly of FIG. 10,illustrating the wheel assembly mounted on the irrigation system of FIG.1 and the tire flexing in response to ground engaging pressure;

FIG. 12 b is a side elevation view of the wheel assembly of FIG. 12 a,the wheel assembly including spacers between wheel spokes and the tire,the spacers limiting the amount the tire flexes in response to theground engaging pressure;

FIG. 13 is a side perspective view of a wheel assembly constructedaccording to another embodiment of the invention, the wheel assemblyincluding a modular airless tire;

FIG. 14 is a fragmented, partially exploded view of the wheel assemblyof FIG. 13;

FIG. 15 is a cross-sectional view of a wheel assembly constructedaccording to another embodiment of the invention, the wheel assemblyincluding a tire presenting a transversely concave outer side;

FIG. 16 a is a fragmented side elevation view of a wheel assemblyconstructed according to another embodiment of the invention, the wheelassembly including a rigid wheel and a flexible airless tire and furtherincluding a plurality of first removable spacers interposed between thewheel and the tire;

FIG. 16 b is a fragmented side view of the wheel assembly of FIG. 16 a,the wheel assembly including a plurality of second removable spacers,the second removable spacers being smaller than the first removablespacers;

FIG. 17 a is a fragmented side elevation view of a wheel assemblyconstructed according to another embodiment of the invention, the wheelassembly including a rigid wheel and a flexible airless tire and furtherincluding a plurality of inflatable spacers interposed between the wheeland the tire, the spacers being inflated to a first, large size;

FIG. 17 b is a fragmented side view of the wheel assembly of FIG. 17 a,the spacers being inflated to a second, small size;

FIG. 18 a is a fragmented side elevation view of a wheel assemblyconstructed according to another embodiment of the invention, the wheelassembly including a rigid wheel and a flexible airless tire and furtherincluding a spacer component with a plurality of inflatable sectionsinterposed between the wheel and the tire, the inflatable sections beinginflated to a first, large size;

FIG. 18 b is a fragmented side view of the wheel assembly of FIG. 18 a,the inflatable sections being inflated to a second, small size;

FIG. 19 is a side perspective view of a wheel assembly constructedaccording to another embodiment of the invention, the wheel assemblypresenting an outer side with a truncated conical shape;

FIG. 20 is an end elevation view of the wheel assembly of FIG. 18;

FIG. 21 is a fragmented, side perspective view of the wheel assembly ofFIG. 18; and

FIG. 22 is a side elevation view of a wheel assembly constructedaccording to another embodiment of the invention, the wheel assemblyincluding a rigid wheel and a flexible airless tire mounted on thewheel, the tire including a plurality of traction lugs of varying size.

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the invention.

DETAILED DESCRIPTION

The following detailed description references the accompanying drawingsthat illustrate specific embodiments in which the invention may bepracticed. The embodiments are intended to describe aspects of theinvention in sufficient detail to enable those skilled in the art topractice the invention. Other embodiments can be utilized and changescan be made without departing from the scope of the present invention.The following detailed description is, therefore, not to be taken in alimiting sense. The scope of the present invention is defined only bythe appended claims, along with the full scope of equivalents to whichsuch claims are entitled.

In this description, references to “one embodiment”, “an embodiment”, or“embodiments” mean that the feature or features being referred to areincluded in at least one embodiment of the technology. Separatereferences to “one embodiment”, “an embodiment”, or “embodiments” inthis description do not necessarily refer to the same embodiment and arealso not mutually exclusive unless so stated and/or except as will bereadily apparent to those skilled in the art from the description. Forexample, a feature, structure, act, etc. described in one embodiment mayalso be included in other embodiments, but is not necessarily included.Thus, the present technology can include a variety of combinationsand/or integrations of the embodiments described herein.

Turning now to the drawing figures, and initially FIG. 1, an exemplaryirrigation system 10 is illustrated including a plurality of wheelassemblies constructed in accordance with embodiments of the invention.The illustrated irrigation system 10 is a central pivot irrigationsystem that broadly comprises a fixed central pivot 12 and a mainsection 14 pivotally connected to the central pivot 12. The irrigationsystem 10 may also comprise an extension arm (also commonly referred toas a “swing arm” or “corner arm”) pivotally connected to the free end ofthe main section.

The fixed central pivot 12 may be a tower or any other support structureabout which the main section 14 may pivot. The central pivot 12 hasaccess to a well, water tank, or other source of water and may also becoupled with a tank or other source of agricultural products to injectfertilizers, pesticides and/or other chemicals into the water forapplication during irrigation.

The main section 14 may comprise a number of mobile support towers16A-D, the outermost 16D of which is referred to herein as an “endtower”. The support towers are connected to the fixed central pivot 12and to one another by truss sections 18A-D or other supports to form anumber of interconnected spans. The irrigation system 10 illustrated inFIG. 1 includes four mobile support towers 16A-D; however, it maycomprise any number of mobile support towers without departing from thescope of the present invention.

Each mobile tower may include a drive tube 20A-D on which a pair ofwheel assemblies 22A-D is mounted. Embodiments of the wheel assemblies22A-D are described in more detail below. A drive motor 24A-D is mountedto each drive tube 20A-D for driving the wheel assemblies 22A-D. Themotors 24A-D may include integral or external relays so they may beturned on, off, and reversed. The motors may also have several speeds orbe equipped with variable speed drives.

Each of the truss sections 18A-D carries or otherwise supports a conduitsection 26A-D or other fluid distribution mechanism that is connected influid communication with all other conduit sections. A plurality ofsprinkler heads, spray guns, drop nozzles, or other fluid-emittingdevices are spaced along the conduit sections 26A-D to apply waterand/or other fluids to land underneath the irrigation system.

The irrigation system 10 may also include an optional extension arm (notshown) pivotally connected to the end tower 16D and supported by a swingtower with steerable wheels driven by a motor. The extension arm may bejoined to the end tower by an articulating pivot joint. The extensionarm is folded inward relative to the end tower when it is not irrigatinga corner of a field and may be pivoted outwardly away from the end towerwhile irrigating the corners of a field.

The irrigation system 10 may also include one or more high pressuresprayers or end guns 28 mounted to the end tower 16D or to the end ofthe extension arm. The end guns 28 may be activated at the corners of afield or other designated areas to increase the amount of land that canbe irrigated.

It will be appreciated that the irrigation system 10 is illustrated anddescribed herein as one exemplary implementation of the wheel assemblies22 described in detail below. Other, equally preferred implementationsof the wheel assemblies 22 not shown or discussed in detail herein mayinclude, without limitation, other types of irrigation systems, such aslateral irrigation systems, other types of agricultural equipment, suchas wagons, carts, implements, and so forth, or other types of vehiclessuch as buses, trucks, and automobiles. However, embodiments of theinvention are especially suited for irrigation systems and othervehicles or systems that travel over un-paved or un-finished ground.

Referring now to FIGS. 2-6, a wheel assembly 22 constructed inaccordance with embodiments of the invention is illustrated. The wheelassembly 22 broadly includes a rigid wheel 30 and a flexible airlesstire 32 mounted on the wheel 30 in a generally circumscribingrelationship to the wheel 30. The wheel 30 and the tire 32 areconfigured such that the tire 32, while being airless, has somecharacteristics of a pneumatic tire that improve the performance of thetire 32. For example, the wheel 30 and tire 32 are configured such thatportions of the tire 32 flex radially inwardly toward the wheel 30 inresponse to ground engaging pressure, as illustrated in FIG. 6. It willbe appreciated that this flexing action increases the total groundengaging footprint of the wheel assembly 22, thus distributing theweight of the wheel assembly 22 and the weight of any machinerysupported by the wheel assembly 22 over a larger area and limiting thetotal amount of ground penetration of the wheel assembly 22.Additionally, penetration of traction lugs or other ground-grippingelements of the tire is limited, as explained below in greater detail.

As used herein, “ground engaging pressure” refers to pressure exerted onthe wheel assembly 22 by the ground when the wheel assembly 22 is atrest on the ground or rolling on the ground. Ground engaging pressuremay include pressure exerted on the wheel assembly 22 from differentdirections or from multiple directions simultaneously, such as where thewheel assembly 22 is on inclined terrain or rolling over an obstacle.Ground engaging pressure is related to the weight of the wheel assembly22 and to the weight of any machinery supported by the wheel assembly22, and thus will vary from one embodiment of the invention to anotherand from one implementation to another.

Generally, the wheel 30 is configured to engage the tire 32 atcircumferentially spaced locations such that portions of the tire 32between the points of engagement flex inwardly in response to groundengaging pressure. In the illustrated embodiment, the wheel 30 includesan innermost hub 34 with a plurality of apertures 36 for attaching to,for example, lug nuts or similar attachment components. A circular ordisc-shaped radial wall 38 or similar structural element connects theinnermost hub 34 with a radially outer cylindrical rim wall 40. The rimwall 40 includes a first shoulder 42 corresponding to a first axialmargin of the rim wall 40, a second shoulder 44 corresponding to asecond axial margin of the rim wall 40, and a substantially flattransverse portion 46 interconnecting the shoulders 42,44. The rim wall40 is generally cylindrical in shape about an axis that corresponds toan axis of rotation of the wheel assembly 22. Thus, the rim wall 40 isgenerally perpendicular or nearly perpendicular to the radial wall 38.

A plurality of mounting elements 48 are approximately equally spacedaround the rim wall 40 and extend radially outwardly from the rim wall40. When the tire 32 is mounted on the wheel 30 the mounting elements 48engage portions of the tire 32 such that the tire 32 is separatedradially from the rim wall 40 by a space, allowing portions of the tire32 to flex inwardly toward the rim wall 40 in response to groundengaging pressure as explained below in greater detail.

In the illustrated embodiment, the wheel assembly 22 includes twelvemounting elements 48 approximately equally spaced around an outerperiphery of the rim wall 40. Each mounting element 48 generallypresents an elongated shape and is oriented transversely on the rim wall40, that is, oriented parallel with the axis of rotation of the wheelassembly 22. Each of the illustrated mounting elements 48 includes afirst side wall 50, a second side wall 52, and an outer wall 54. Whileeach of the illustrated mounting elements 48 includes substantiallyflat, rectangular side walls 50,52 and outer wall 54, it will beappreciated that the particular size and shape of the mounting elements48 is not important to the invention and may vary from one embodiment toanother without departing from the spirit or scope of the invention. Byway of example, each of the mounting elements 48 may be defined by asingle, continuous rounded wall or a plurality of separate elementspositioned to cooperatively perform the functions of the spacer elements48 as described herein.

As explained above, the illustrated embodiment of the wheel assembly 22includes twelve mounting elements 48 approximately equally spaced alongan outer circumference of the wheel 30, or separated by an angle ofapproximately thirty degrees. Thus, if the rim wall 40 is aboutforty-eight inches in diameter, the mounting elements 48 are spacedapproximately twelve and one-half inches apart. If the rim wall 40 isabout fifty inches in diameter, the mounting elements 48 are spacedapproximately thirteen inches apart. If the rim wall 40 is abouttwenty-four inches in diameter, the mounting elements 48 are spacedapproximately six inches apart. These are but a few examples.

Each mounting element 48 is configured to engage the flat transverseportion 46 of the rim wall 40 and each of the first 42 and second 44shoulders of the rim wall 40. End caps 56 may be placed on opposing endsof each mounting element 48 and secured in place with a fastener, suchas a nut and bolt combination or similar fastener. Each end cap 56includes a pair of flanges 58 for engaging drive lugs of the tire 32 toprevent lateral movement of the tire 32 relative to the wheel 30. Eachpair of flanges 58 extends laterally relative to the respective mountingelement 48, longitudinally relative to the rim wall 40. The end caps 56may also perform other functions, such as preventing soil and debrisfrom entering the mounting elements 48. The illustrated mountingelements 48 are constructed separately from the wheel 30 and may bewelded or otherwise bonded or attached to the wheel 30. Alternatively,the mounting elements 48 may be integrally formed as part of the wheel30.

The tire 32 is configured to be mounted on the wheel 30 such that atleast a portion of the tire 32 engages the mounting elements 48 and thetire 32 presents a generally circular or nearly circular outer profile.Advantageously, the wheel 30 is configured for use with an airless tire.As used herein, a “tire” is a flexible component positioned andconfigured to engage the ground during use of the wheel assembly 22. An“airless tire” is a tire that does not require trapped or compressed airfor normal and proper use. An airless tire may be constructed of asingle, unitary piece of material or multiple pieces of material. Forpurposes of this document, a tire used with inflatable spacers(explained below) is considered airless if the tire does not otherwiseuse or require trapped or compressed air for normal and proper use, evenif the inflatable spacers are attached to or integral with the tire.

The illustrated tire 32 is generally cylindrical in shape with aplurality of traction lugs 60 extending radially outwardly from an outerside 62 of the tire 32 and a plurality of drive lugs 64, spacers 66, orboth extending radially inwardly from an inner side 68 of the tire 32.The outer side 62 of the tire 32 is generally transversely flat, thatis, the outer side 62 of the tire 32 presents little or no curvaturefrom a first edge 70 of the tire 32 to a second edge 72 of the tire 32.Similarly, the inner side 68 of the tire 32 is also generallytransversely flat.

The traction lugs 60 engage the ground and help prevent the wheelassembly 22 from slipping relative to the ground. The illustratedtraction lugs 60 are generally rectangular in shape and transverselyoriented on the tire 32, are integrally formed with the tire 32 and maybe approximately equally spaced circumferentially around the outer side62 tire 32. As illustrated in FIG. 6, the tire 32 may be configured suchthat each traction lug 60 is positioned intermediate two consecutivemounting elements 48. This configuration allows the portion of the tire32 bearing the traction lug 60 to flex inwardly in response to groundengaging pressure. This performance characteristic allows each tractionlug 60 to engage the ground, yet limits the amount of ground penetrationaccording to the amount of inward flex permitted by the spacer 66. Itmay be desirable in some implementations to position the traction lugs60 proximate or in direct radial alignment with the mounting elements48. Such alternative configurations of the tire 32 are within the ambitof the present invention.

The drive lugs 64 engage the wheel 30 and prevent the tire 32 fromslipping on the wheel 30. In the illustrated embodiment, each of thedrive lugs 64 is integrally formed in the tire 32 and presents agenerally elongated body with a triangular cross section, transverselyoriented on the tire 32. A pair of drive lugs 64 engages either side ofeach mounting element 48, wherein sides of the drive lugs 64 areconfigured and angled for optimal contact with the angled side walls50,52 of the mounting elements 48. Because a drive lug 64 is positionedon each side of each mounting element 48, the drive lugs 64 engage themounting element 48 and prevent the tire 32 from rotating relative tothe wheel 30 regardless of whether the wheel 30 is moving in a forwardor reverse direction. Similarly, the flanges 58 of the mounting elementend caps 56 engage axial ends of the drive lugs 64 and prevent the tire32 from shifting axially relative to the wheel 30.

The plurality of spacers 66 extend inwardly from the inner side 68 ofthe tire 32 and regulate the amount of inward flex of the tire 32. Inthe illustrated embodiment, the spacers 66 are integrally formed as partof the tire 32 and are similar in size and shape to the drive lugs 64,and each spacer 66 is positioned to be in radial alignment with one ofthe traction lugs 60. As best illustrated in

FIG. 6, as the tire 32 flexes inward in response to ground engagingpressure, a spacer 66 limits the inward flex as the spacer 66 contactsthe rim wall 40. While the spacers 66 of the illustrated embodiment aresimilarly configured to the drive lugs 64, it will be appreciated thatthe spacers 66 may be of various sizes and shapes without departing fromthe spirit or scope of the present invention.

Particularly, the spacers 66 may be configured according to a particularsize to allow the tire to flex inwardly a desired amount. Similarly, thespacers 66 need not be aligned axially with the traction lugs 60, butmay be offset from the position in the illustrated embodiment. Such aconfiguration may be desirable, for example, to further regulate theperformance of the traction lugs 60 when the tire 32 flexes in responseto ground engaging pressure.

The tire 32 may be configured such that as the tire 32 flexes inwardlytoward the wheel 30, the flexed portion of the tire 32 remainstransversely flat or substantially transversely flat. This may bedesirable, for example, to preserve a wide footprint or otherwise limitthe amount of ground penetration.

The tire 32 may be mounted on the wheel 30 according to any of variousmethods. For example, the tire 32 may be press fitted to the wheel 30,wherein the tire 32 must be expanded or stretched to be placed over thewheel 30 and remains partially stretched while mounted on the wheel 30.If the tire 32 is press fitted to the wheel 30, tension remaining in thetire 32 after it is mounted on the wheel 30 helps retain the tire 32 onthe wheel 30, in addition to the mounting element end caps 58, asexplained above. Alternatively, the tire 32 may be loose fitted on thewheel 30, wherein the tire 32 is of an appropriate size relative to thewheel 30 that the tire 32 need not be stretched for placement on thewheel 30 but may be slid onto the wheel 30. If the tire 32 is loosefitted to the wheel 30, little or no tension remains in the tire 32 onceit is mounted on the wheel 30 such that the mounting element end caps 58or similar elements may be required to hold the tire 32 in place on thewheel 30. In some embodiments, the tire 32 may be bonded to the wheel30, although bonding presents some disadvantages, namely, the tire 32cannot be easily removed for repair or replacement.

The tire 32 is constructed of a flexible material, such as rubber, PVCor plastic. The tire 32 may further include reinforcing elements thatlimit stretch and strengthen the tire 32. Such reinforcing elements mayinclude, for example, fabric webbing or steel belts. The tire 32 may besufficiently resilient that it retains a circular shape along portionsof the tire 32 not supported by the mounting elements 48.

The wheel 30 is constructed of a rigid material such as, for example,metal, plastic or a composite material. The size of the wheel assembly22 may vary substantially from one embodiment of the invention toanother without departing from the scope of the invention. Dimensionsand ranges of various preferred embodiments will now be discussed withthe understanding that the dimensions and ranges are exemplary, and notlimiting, in nature. The diameter of the wheel 30, including themounting elements 48, is preferably within the range of from abouttwenty-four inches to about sixty inches and more preferably within therange of from about thirty-six inches to about forty-eight inches. Thewidth of the wheel 30 is preferably within the range of from about sixinches to about eighteen inches and more preferably within the range offrom about eight inches to about sixteen inches. The height of themounting elements 48 is preferably within the range of from about oneinch to about four inches, more preferably within the range of fromabout two inches to about three inches.

The thickness of the tire 32, excluding the traction lugs 60, ispreferably within the range of from about one-half inch to about threeinches, more preferably within the range of from about one inch to abouttwo inches. The height of the traction lugs 60 is preferably within therange of from about one-quarter inch to about four inches, morepreferably within the range of from about one-half inch to about threeinches. In one exemplary embodiment, the wheel assembly 22 is abouteleven inches wide and about fifty-two inches in diameter.

Turning now to FIGS. 7-9, a wheel assembly 100 constructed according toan alternative embodiment of the invention is illustrated. The wheelassembly 100 is similar in size, shape and function to the wheelassembly 22 described above, except that the wheel assembly 100 includesa wheel 102 with a radially outer rim wall 104 presenting a polygonalshape.

The wheel 102 includes an innermost hub 106 with a plurality ofapertures 108 for attaching to, for example, lug nuts or similarattachment components. A disc-shaped radial wall 110 or similarstructural element extends radially outwardly from the hub 106 andincludes peripheral apertures 112 for attaching to elements of the rimwall 104.

The rim wall 104 is defined by a plurality of outermost vertices 114connecting a plurality of planar faces 116. In the illustratedembodiment, the rim wall 104 is defined by twelve vertices 114connecting twelve faces 116. The rim wall 104 comprises eight sections118, including four sections 118 a corresponding to a first side of thewheel 102 and four sections 118 b corresponding to a second side of thewheel 102. Each section 118 defines a portion of each of threeconsecutive faces and a portion of a lug aperture 120. Each section 118a cooperates with a corresponding section 118 b from the opposite sideto fully define the three consecutive faces and the lug aperture. Eachsection 118 also includes one or more inwardly-extending flangescorresponding to an axially inner edge of the section 118 and includingattachment apertures 124 corresponding to the peripheral apertures 112of the radial wall 110 for attaching the sections to the radial wall110.

When the wheel 102 is assembled the vertices 114 are the outermoststructural elements of the wheel 102. The wheel 102 is configured suchthat the tire 126 engages and is supported by the vertices 114 of therim wall 104 and portions of the tire 126 between the vertices 114 areseparated from the faces 116 by a space. Portions of the tire 126between the vertices 114 are configured to flex inwardly toward thefaces 116 in response to ground engaging pressure, as illustrated inFIG. 9 a. The wheel 102 need not include mounting elements, as the tire126 is mounted on the vertices 114 of the rim wall 104. The lugapertures 120 are used to secure the tire 126 to the wheel 102 such thatthe tire 126 does not rotate or shift laterally relative to the wheel102.

A plurality of spacers 128 may be interposed between the wheel 102 andthe tire 126 to regulate the degree to which the tire 126 flexes inresponse to ground engaging pressure. In particular, the spacers 128 maybe positioned on the faces 116 at approximately a midpoint betweenconsecutive vertices 114 where separation of the tire 126 from the wheel102 is the greatest. As illustrated in FIG. 9 b, the spacers 128 areattached to the wheel 102 and, as explained below, may be removablyattached to the wheel 102.

The tire 126 is similar to the tire 32 described above, except that thetire 126 includes four drive lugs 130 for engaging the drive lugapertures 120 of the rim wall and may not include spacer elementsattached thereto or integrally formed in the tire 126. The four drivelugs 130 may be integrally formed with the tire 126 and areapproximately equally spaced around an inner side 132 of the tire 126.The drive lugs 130 are configured and positioned to engage the lugapertures 120 of the wheel 102. The tire 126 may be positioned on thewheel 102 such that each traction lug 130 is positioned approximatelyover a center of a face 116 and in radial alignment with a spacer 128,if spacers are present.

Turning now to FIGS. 10-12, a wheel assembly 200 constructed accordingto another embodiment of the invention is illustrated. The wheelassembly 200 is similar to the wheel assembly 100 described above,except that the wheel assembly 200 includes a wheel 202 defined by a huband spoke configuration. In particular, the wheel 202 comprises a hub204 and a plurality of spoke elements 206 extending radially outwardlyfrom the hub 204. The hub 204 includes an inner hub ring 208 with aplurality of apertures 210 for attaching to, for example, lug nuts orsimilar attachment components. A disc-shaped radial wall 212 or similarstructural element extends radially outwardly from the inner hub ring208. The radial wall 212 includes a plurality of outer peripheralapertures 214 for attaching the plurality of spoke elements 206 to theradial wall 212. The spoke elements 206 extend radially outwardly fromthe radial wall 212 and support the tire 216.

The illustrated embodiment includes six spoke elements 206 approximatelyequally spaced around the radial wall 212. Each spoke element 206includes a planar radial portion 218 and a planar transverse portion 220that together form a T-shaped cross section. The planar radial portion218 attaches to the radial wall 212 and extends radially outwardlytoward the transvers portion 220. Each transverse portion 220 representsa radially outer, rectangular planar face that lies in a plane that isapproximately parallel with an axis of rotation of the wheel assembly200.

The tire 216 may be similar to the tire 126 described above. The tire216 is mounted on the spoke elements 206 and engages opposing forward222 and trailing 224 edges of the transverse portion 220 of each spokeelement 206. The edges 222,224 support the tire 216 and portions of thetire 216 between consecutive spoke elements 206 and between the edges222,224 of each spoke element 206 flex inwardly toward a center of thewheel 202 in response to ground engaging pressure, as illustrated inFIG. 12 a. Spacers 226 may be placed between the spoke elements 206 andthe tire 216, as illustrated in FIG. 12 b, thus limiting the amount ofinward flex of the tire toward the face of each spoke element.

Portions of the tire 216 between the spoke elements 206 may flexinwardly more than portions of the tire 216 corresponding to the spokeelements 206, particularly if spacers 226 are present on the spokeelements 206. This may result in traction lugs 228 positioned inalignment with the spoke elements 206 experience greater groundpenetration than traction lugs 228 positioned between the spoke elements206.

A first, outer diameter of the wheel 202 including the spoke elements206 is greater than a second, inner diameter of the wheel 202 notincluding the spoke elements 206. By way of example, the inner diametermay be about 25% of the outer diameter, may be about 50% of the outerdiameter, or may be about 75% of the outer diameter.

Turning now to FIGS. 13-14, a wheel assembly 300 constructed accordingto another embodiment of the invention is illustrated. The wheelassembly 300 is similar in size, shape and function to the wheelassembly 100 described above, except that the wheel assembly 300includes a wheel 302 with a plurality of attachment points 304 forattaching modular portions of a tire 306 to the wheel 302. Moreparticularly, the wheel 302 includes four attachment points 304approximately equally spaced around a radially outer rim wall 308 of thewheel 302. Each attachment point 304 corresponds to a vertex of the rimwall 308 and includes an aperture 310 and a pair of eyelets 312. Theeyelets 312 are positioned in axial alignment on opposing axial marginsof the rim wall 308 to receive a pin 314.

The tire 306 is similar in size and shape to the tire 126 describeabove, except that the tire 306 comprises a plurality of separate tiresections 316,318,320,322. Each of the tire sections 316-322 correspondsto a circumferential portion of the tire 306, in the illustratedembodiment each section 316-322 corresponds to about one-fourth of thecircle defined by the tire, or about ninety degrees of curvature of thetire 306. The tire sections 316-322 may be removably attached to thewheel 302 and, when attached to the wheel 302, generally form a circularshape in circumscribing relationship to the wheel 302.

Each of the tire sections 316-322 may be identically configured,therefore only section 316 will be described in further detail with theunderstanding that the other sections 318,320,322 may be similarly oridentically configured. A first end 324 of the section 316 and a secondend 326 of the section 316 each include a plurality of loops 328 inaxial alignment and configured to receive a pin 314. When the tiresection 316 is attached to the wheel 302, the loops 328 of the first end324 are interdigitated with end loops 328 of section 318 and positionedin axial alignment with the eyelets 312 of the attachment point 314 andthe end loops 328 of section 318 such that a pin 314 may be insertedthrough the eyelets 312 and the loops 328 of both sections 316,318,thereby securing the loops 328 in place. The second end 326 of thesection 316 is similarly secured to an attachment point 304 with an endof section 322.

Because each tire section 316-322 is secured to the wheel 302 via a pin314, drive lugs are not necessary. Thus, an inner side of each of thetire sections 316-322 may be substantially smooth while an outer sidemay include traction lugs 330 similar to the traction lugs 60 describedabove. While the illustrated modular tire 306 includes four sections316-322, it will be appreciated that the tire 306 may comprise more thanfour sections or fewer than four sections. By way of example and notlimitation, the modular tire 306 may include only two sections, threesections, or five sections. Furthermore, the wheel assembly 300 mayinclude spacers (not shown) positioned between the tire 306 and thewheel 302 to regulate the flexing action of the tire 306. Such spacersmay be attached to the wheel 302 or the tire 306.

FIG. 15 illustrates a wheel assembly 400 constructed according toanother embodiment of the invention. The wheel assembly 400 is similarin size, shape and function to the wheel assembly 22 described above,except that the wheel assembly 400 includes a tire 402 with an outerside 404 that is transversely concave. In other words, the outer side404 of the tire 402 presents a concave profile between a first edge 406and a second edge 408. The tire 402 also differs from the tire 32 inthat the tire 402 does not include traction lugs. In the illustratedembodiment, the concave profile results from the tire 402 being thickeron the edges 406,408 than in a middle portion between the edges 406,408.Such a configuration may be desirable, for example, to prevent thelateral displacement of soil beneath the tire 402.

Turning now to FIGS. 16-18, a wheel assembly 500 constructed accordingto another alternative embodiment of the invention is illustrated. Thewheel assembly 500 includes a wheel 502 and a tire 504 and is similar tothe wheel assembly 22 described above, except that the wheel assembly500 includes spacers that are interchangeable, adjustable, or both.Removing, exchanging or adjusting the spacers may be desirable to adjustthe amount the tire flexes. If the wheel assembly 500 will be used in anenvironment with softer ground, it may be desirable to use smallerspacers that allow greater inward flex to increase the ground engagingfootprint of the wheel assembly 500, decrease penetration of thetraction lugs, or both. Similarly, if the wheel assembly 500 will beused in an environment with harder ground, it may be desirable to uselarger spacers that allow less inward flex to decrease the groundengaging footprint of the wheel assembly 500, increase penetration ofthe traction lugs, or both.

In a first configuration illustrated in FIGS. 16 a and 16 b, the wheelassembly 500 includes interchangeable spacers 506,508. A first set ofspacers 506 are larger and may be removed and replaced with a second,smaller set of spacers 508. Each of the spacers 506,508 is elongatedwith a generally rectangular cross section and is oriented generallytransversely on the wheel 502. The spacers 506,508 may be removablyattached to the wheel 502 using any of various removable fasteners suchas, for example, a nut and bolt combination.

In a second configuration illustrated in FIGS. 17 a and 17 b, the wheelassembly 500 includes adjustable spacers 510. The spacers 510 aresecured to the wheel 502 in radial alignment with the traction lugs andare adjustable between a first, larger size (FIG. 17 a) and a second,smaller size (FIG. 17 b). Adjusting the spacers between the first sizeand the second size may be performed without removing the spacers 510from the wheel assembly 500. By way of example, the adjustable spacers510 may be inflatable such that inflating the spacers 510 causes them toenlarge and deflating the spacers causes them to decrease in size.Alternatively or additionally, adjusting the air pressure in the spacers510 may alter the hardness or flexibility of the spacers 510, such thatincreasing air pressure hardens the spacers 510 and decreases the amountof inward flex of the tire 504 and decreasing air pressure softens thespacers 510 and increases the amount of inward flex of the tire 504.

Each of the spacers 510 is adjustable separately from the other spacers,wherein each of the spacers 510 may include a valve and valve stem (notshown) similar or identical to a conventional valve and a valve stemused on a pneumatic tire. Alternatively, a single spacer component 512with a plurality of inflatable sections 514 may be used. The spacercomponent 512 functions similarly to spacers 510, except that theinflatable sections 514 are in fluid communication such that all of thesections 514 are inflated simultaneously as a single unit. A recess orbreak in each of the mounting elements 516 my accommodate a portion ofthe spacer component 512 enabling fluid communication between sections514. For example, the spacer component 512 may take the form of aninflatable tube with a single inflatable chamber comprising all of thesections 514. Alternatively, the inflatable sections 514 may beinterconnected via rigid channels in the spacer component 512 thatpermit fluid flow therethrough.

It will be observed that the combination of the tire 504 and the singlespacer component 512 described above is similar in some respects to atraditional pneumatic tire or tube/tire assembly in form and function.Specifically, the spacer component 512 is configured to be inflated anddeflated as a single unit, is interposed between the tire and the wheel,and regulates the inward flex of portions of the tire during operation.One notable difference between the wheel assembly 500 with the spacercomponent 512 and a conventional pneumatic tire is that the tire 504 issupported by the mounting elements 516 and the spacer component 512 onlyregulates the inward flex of certain portions of the tire 504. Anothernotable difference between the wheel assembly 500 with the spacercomponent 512 and a conventional pneumatic tire is that the wheelassembly 500 is configured for normal operation even if the spacercomponent 512 is completely deflated. Thus, if the spacer component 512should become damaged or otherwise deflate unexpectedly during use, thewheel assembly 500 would continue to operate without sustaining damageand with minimal impact on the performance of the wheel assembly 500.

Turning now to FIGS. 19-21, a wheel assembly 600 constructed accordingto another alternative embodiment of the invention is illustrated. Thewheel assembly 600 includes wheel 602 that is similar to the wheel 30except that the wheel 602 does not have mounting elements. The wheelassembly 600 also includes a tire 604 that is similar to the tire 32except that the tire 604 does not include spacer elements or drive lugs,and the tire 604 presents a truncated conical outer shape wherein afirst edge 606 of the tire 604 presents a larger outer diameter than asecond edge 608 of the tire 604. An outer side 610 of the tire 604slopes radially inwardly from the first edge 606 to the second edge 608along a straight or arcuate path.

The truncated conical configuration may be achieved through designconfigurations associated with the wheel 602, the tire 604 or both. Inthe illustrated embodiment, the wheel 602 includes a radially outer rimwall 612 similar or identical to the rim wall 40 described above,wherein the rim wall 612 defines a cylinder about an axis thatcorresponds to an axis of rotation of the wheel assembly 600. The rimwall 612 includes first 614 and second 616 shoulders and a transverseportion 618 intermediate the shoulders 614,616. The tire 604 isconfigured such that a first axial margin of the tire 604 correspondingto the first edge 606 rests on the first shoulder 614 and is separatedfrom the transverse portion 618 by a space. A second axial margin of thetire 604 corresponding to the second edge 608 rests in part on thetransverse portion 618 of the rim wall 612 proximate the second shoulder616. This is but one, exemplary configuration of the wheel assembly 600.

The slope of the outer side 610 of the tire 604 relative to the axis ofrotation of the wheel assembly 600 is preferably within the range offrom about 0.01 to about 1.0, and more preferably within the range offrom about 0.05 to about 0.5 and may particularly be about 0.1, about0.2 or about 0.3. By way of example, the width of the tire 604 may beabout eleven inches, the first edge 608 may be about fifty-one inches indiameter and the second edge 606 may be about fifty three inches indiameter.

The truncated conical configuration of the embodiment illustrated inFIGS. 19-21 may be desirable, for example, where the wheel is used on asloped surface or otherwise is not perpendicular with the surface of theground.

FIG. 21 illustrates a wheel assembly 700 constructed according toanother alternative embodiment of the invention. The wheel assembly 700may be similar or identical to the wheel assembly 22 described above,except that the wheel assembly 700 includes some traction lugs 702 of afirst configuration and some traction lugs 704 of a secondconfiguration. More particularly, the wheel assembly 700 includes atotal of twelve traction lugs, wherein three of the traction lugs 704are larger than the remaining nine traction lugs 702. The largertraction lugs 704 have a greater radial reach than the smaller tractionlugs 702, such that the larger traction lugs 704 may experience greaterground penetration than the smaller traction lugs 702. This may bedesirable, for example, on soft or muddy ground where the wheel assembly700 is susceptible to slipping on the ground.

Although the invention has been described with reference to theexemplary embodiments illustrated in the attached drawings, it is notedthat equivalents may be employed and substitutions made herein withoutdeparting from the scope of the invention as recited in the claims. Forexample, the interchangeable and adjustable spacers 506,508,510 may beused with any of the embodiments of the wheel assembly described herein.Furthermore, spacers may be entirely omitted from any of the embodimentsof the wheel assembly described herein. Additionally, any number oftraction lugs may be used with the various embodiments of the wheelassembly, the traction lugs may be of virtually any size and shape, anda conventional tire tread may be used instead of traction lugs.

Having thus described various embodiments of the invention, what isclaimed as new and desired to be protected by Letters Patent includesthe following:
 1. A wheel assembly comprising: a rigid wheel includingan outer rim wall presenting a polygonal shape with a plurality ofoutermost vertices connecting a plurality of planar faces; and aflexible tire mounted on the outer rim wall such that the tire issupported by the vertices of the rim wall and is separated from the rimfaces by a space, portions of the tire located between the verticesbeing configured to flex inwardly when subject to ground engagingpressure.
 2. The wheel assembly of claim 1, the tire include a pluralityof traction lugs extending radially outwardly from an outer surface ofthe tire, the traction lugs spaced circumferentially around the tire andlocated between the vertices such that the traction lugs move inwardlywith the portions of the tire configured to flex inwardly when subjectto ground engaging pressure.
 3. The wheel assembly of claim 2, whereinone of the plurality of traction lugs is larger than adjacent tractionlugs.
 4. The wheel assembly of claim 1, each of the faces of the outerrim wall being parallel with an axis of rotation of the wheel.
 5. Thewheel assembly of claim 1, further comprising a plurality of spacers,each spacer positioned on one of the faces and configured to limit theamount of inward flex of the tire.
 6. The wheel as set forth in claim 1,the tire presenting an outer side with a truncated cone shape.
 7. Thewheel assembly of claim 1, the tire being cylindrical in shape andpresenting a transversely flat outer side.
 8. The wheel assembly ofclaim 1, the tire being cylindrical in shape and presenting atransversely concave outer side.
 9. The wheel assembly of claim 1, thetire being a single, solid piece of material of unitary construction.10. The wheel assembly of claim 1, the tire being of modularconstruction including at least two sections secured to the wheel toform the tire.
 11. A wheel assembly comprising: a rigid wheel includingan inner hub and a plurality of spoke elements extending radiallyoutwardly from the hub; and an outer flexible airless tire mounted onthe wheel such that the tire is supported by the spoke elements,portions of the tire located between the spoke elements being configuredto flex inwardly when subject to ground engaging pressure.
 12. The wheelassembly of claim 11, the tire include a plurality of traction lugsextending radially outwardly from an outer side of the tire, thetraction lugs spaced circumferentially around the tire and located onthe portions of the tire configured to flex inwardly when subject toground engaging pressure.
 13. The wheel assembly of claim 11, the hubpresenting an outer diameter that is less than 75% of the outer diameterof the wheel.
 14. The wheel assembly of claim 11, the hub presenting anouter diameter that is less than 50% of the outer diameter of the wheel.15. The wheel assembly of claim 11, each of the spoke elementspresenting a planar outer face wherein a portion of the tire proximatethe face is separated from the face by a space and is configured to flexinwardly toward the face in response to ground engaging pressure. 16.The wheel assembly of claim 15, further comprising a plurality ofspacers, each spacer positioned between the tire and one of the outerfaces and configured to limit the amount of inward flex of the tire. 17.A mobile irrigation system tower comprising: a structure for supportingan irrigation system conduit; and a plurality of wheel assembliessupporting the structure, each wheel assembly including a rigid wheelincluding a radially outer rim wall presenting a polygonal shape with aplurality of outermost vertices connecting a plurality of planar faces;and a flexible airless tire mounted on the outer rim wall such that thetire is supported by the vertices of the rim wall and is separated fromthe rim faces by a space, portions of the tire located between thevertices being configured to flex inwardly when subject to groundengaging pressure.
 18. The mobile irrigation system tower of claim 17,the flexible tire including a plurality of traction lugs extendingradially outwardly from an outer surface of the tire, the traction lugsspaced circumferentially around the tire and located between thevertices of the rim wall such that the traction lugs move inwardly withthe portions of the tire configured to flex inwardly when subject toground engaging pressure.
 19. The wheel assembly of claim 17, furthercomprising a plurality of spacers, each spacer positioned between twoconsecutive vertices of the rim wall and configured to limit the amountof inward flex of the tire.
 20. The wheel assembly of claim 17, the tirebeing of modular construction including at least two sections secured tothe wheel to form the tire.